The head of Iran's Chamber of Commerce, Mohammad Nahavandian, rejected the move as "unjustifiable", saying such sanctions would have reciprocal consequences.

"The Iranian nation and those involved in trade and economic activities will find other alternatives," said Nahavandian.

Washington and the European Union have already pushed four rounds of sanctions through the United Nations over Iran's nuclear program and imposed unilateral measures that have deterred Western investment in Iran's oil sector, making it harder to move money in and out of the country.

Imposing sanctions on the central bank would tighten that screw and make it more difficult for Iran to receive payments for exports -- particularly oil, a vital source of hard currency for the world's fifth-biggest crude exporter.

Iranian officials insist that foreign sanctions have had no impact on the country's economy.

"The sanctions have raised the cost of trade and economic transactions but it has not managed to change Iran's political behavior," Nahavandian said.

So far, Iran's leaders have shown no sign of changing the country's nuclear course despite mounting international pressure to force it to stop.

US financial institutions are already generally prohibited from doing business with any bank in Iran, including the central bank, so the new measure by Washington would have to be carried out with international agreement.

Nahavandian said European countries should not miss the investment opportunity in an emerging market like Iran.

"Considering the economic crisis in Europe, the European companies are
after finding new markets ... political disputes should not have an
impact on trade relations," he said.

Senior US officials said Washington was engaging with its foreign
partners to ensure the sanctions can work without harming global energy
markets and stressed the US strategy for engaging with Iran was
unchanged by the bill.